This invention relates to the operation of dishwashers, and more specifically to relieving of overpressure caused by normal operation. Normal operation of a dishwasher causes a condition, referred to as overpressure, at the start-up of a wash cycle or when the wash cycle is interrupted and then restarted. Hot water thrown into the air by the wash system rapidly heats the air inside of the washer chamber causing the air to expand, thus increasing internal pressures. This overpressure happens at varying degrees at the beginning of each wash cycle. Failure to relieve this pressure may result in gasket blowouts or undesirable water leaks. Thus, of necessity, there must be a venting means provided in a dishwasher to prevent these adverse consequences. Typical overpressure venting means are through the drying system outlet vent or a water injector port.
Another concern relating to the relief of overpressure is the problem created by the suds from the dishwasher in normal operation, or, should laundry detergent be accidentally substituted for automatic dishwasher detergent. Traditionally, the inlet port for the drying system is located in the bottom of the washing chamber of the dishwasher. This area, being near water level, is subject to sudsing during wash. Thus, any vent located in the bottom of the washing chamber must prevent suds from going through the drying system inlet port or chimney. Conventional dishwashers, such as that described in U.S. Pat. No. 4,247,158, provide a cap or valve that seals on the chimney to prevent suds from passing during the washing cycle and which is lifted during the drying cycle to allow drying air to flow into the chamber when the blower motor is actuated.